The invention relates to the field of surgical biopsy instruments.
A biopsy instrument is frequently used to obtain a piece of tissue for microscopic examination to determine malignancy, while subjecting the patient to the least trauma. Typically, the instrument consists of a long, thin probe, termed a stylet, within a close-fitting hollow needle, termed a cannula. The stylet and cannula are contained within a firing device that first projects the stylet into the tumor, followed immediately by the cannula. The stylet has a notch into which tissue will prolapse when the stylet enters the tumor. As the cannula slides over the stylet, a small piece of tissue is then severed from the tumor mass and captured within the notch of the stylet. The instrument is then withdrawn and the piece of tissue removed from the stylet.
Lindgren, U.S. Pat. No. 4,699,154, describes a biopsy needle instrument which projects the stylet and the cannula sequentially when the firing button is pushed. That instrument requires that the physician load both the stylet and the cannula at the same time by compressing the stylet and cannula springs simultaneously.